The objective of the proposed research is to understand neural mechanisms underlying vocal production in the primate brain and their implications for human speech processing mechanisms in normal and pathological conditions. Earlier studies concluded that the cerebral cortex plays little role in vocal production in non-human primates, which is in sharp contrast to the role of human cortex in speech production and inconsistent with accumulating evidence from the past two decades. In this application, we will re-examine this important question using a highly vocal primate, the common marmoset (Callithrix jacchus), as our experimental model. The marmoset provides a unique advantage over other non-human primate species typically used in laboratory studies in that it as a rich vocal repertoire and interesting vocal behaviors that are readily studied in laboratory conditions. In Aim 1, we will identify frontal cortex areas associated with vocal production in marmosets. The proposed experiments in this aim will take the advantage of a unique vocal behavior ("antiphonal calling") and a well-developed chronic recording technique to identify specific cortical areas in the marmoset brain involved in vocal production. Aim 2 will study physiological properties of neurons in the frontal cortex during vocal exchanges in freely roaming marmosets using a wireless recording technique. Experiments in this aim will help identify the network of cortical areas in the marmoset brain that are responsible for generating and controlling vocalizations. Aim 3 will examine the roles of specific frontal cortex areas in controlling vocal production using reversible inactivation methods. Findings from the proposed study will shed lights on neural mechanisms responsible for vocal production in the primate brain and have implications for understanding how the brain operates during speaking and hearing. PUBLIC HEALTH RELEVANCE: How the brain processes speech is of the fundamental importance to the well-being of everyone in the society, but remains largely unknown to date. Findings of the present study will contribute to our understanding of neural mechanisms underlying vocal production in the primate brain. They will have important implications for understanding human speech production mechanisms in normal and pathological conditions. .